Japanese Chief Cabinet Secretary Katsunobu Kato said on Tuesday said: “The Chinese ships entered the Japanese territorial waters on October 11. “They continue to remain there, for more than two days already. This is extremely unfortunate.
China has been testing the resolve of nations to defend their maritime waters for some time now.
Beijing has deployed its naval vessels in disputed territory n the South China Sea causing tensions to rise in the region.
The last time Chinese vessels were in Japanese waters was in July, the vessels remained for 39 hours.
The islands may sit above extensive mineral resources below the seabed.
In 2012 the Japanese government purchased three of the five islands from the private owner to ensure they had sovereign control.